1. Field of the Invention
The present invention relates to the field of air defense against missiles, e.g., by means of projectiles and relates to a method for increasing the probability of success by means of an intended fragmentation of a specially designed projectile.
2. Description of Background and Material Information
Missiles are unmanned aerial objects, such as rockets, guided bombs, projectiles and drones. The spectrum of possible movements of such objects is greatly varied. The means for defense against them are correspondingly varied; they extend from simple air defense launchers to complex air-to-air weapons with target-seeking heads. Installations for defending against and destroying enemy missiles by means of projectiles, which are the subject of this application, essentially include at least one launching tube or gun for launching the projectile and a fire control device for measuring the movement of the missile and calculating the launching direction and the time for triggering. Automatic fire control is indispensable for defense against fast and maneuverable missiles, i.e., tracking of the target, in the case of a missile, and calculation of the launching direction takes place continuously on the basis of the results of the tracking, and guidance of the gun is continuously readjusted. If desired, the timing and the lenqth of the salvo can also take place automatically, once the inhibition of the launching command has been removed.
The general problem of aircraft or missile defense consists in bringing a sufficiently large destructive potential at the right time to the instantaneous position of the object to be combatted and to make it become effective there. In the simplest instance, the destructive potential consists in the moved mass of a ballistic projectile, i.e., in kinetic energy. So that it can become effective, the projectile or at least a portion of it must hit the target. Another possibility is an explosive projectile which carries explosive matter, i.e., latent chemical energy, which detonates in case of a direct hit or with the aid of a proximity fuse, and has its destructive effect in heat radiation and pressure waves.
However, the defense task consists in rendering the object harmless, i.e., to destroy it, to steer it away from its dangerous course or to damage it in such a way that it can no longer fulfill its purpose. In this connection, it does obviously make a difference where the object is hit (or at what distance from the object the charge detonates) and how the destructive energy is transmitted. Although a clean shot through a stabilizer is a hit, it remains without effect, the same as an exactly placed load of the smallest shot pellets, none of which is able to penetrate the hull of the object.
The design of the munitions and consideration of the probabilities of destruction of the object for various impact positions must be included in missile defense calculations. However, the initial point of departure is that the impact problem of the defense is basically solved if:
from the target tracking until the firing of the projectile, the target trajectory during the flight time of the projectile is known; PA1 the trajectory of the projectile with respect to a set direction of departure is known from the knowledge of ballistics; PA1 the guidance data for the gun for scoring a hit are known from the fire control calculations on the basis of the above information, and PA1 after launch, the expected meeting point between projectile and target in space and the time of the impact are known.
However, in actuality the target and projectile will hardly meet at the calculated place. Calculations are based on extrapolations which naturally include uncertainties. The uncertainty regarding the position of the projectile at the calculated time of the impact results from aiming errors and the spread or range of the gun, the spread or range of the initial velocity of the projectile and external ballistic disturbances, for example the effect of wind. The uncertainty regarding the position of the target at the calculated time of the impact results from the limited measuring accuracy during target tracking, the inherent variance of the prediction algorithm and the maneuvers of the target not detected in the meantime. Thus there is the problem of an insufficient hit and destruction probability on account of these uncertainties, in short, the unsatisfactory probability of success of the missile defense, which needs to be improved by suitable means.
A known measure for increasing the probability of success consists in time-imprinting of the projectile. Immediately at the time of launching, the projectile is time-imprinted, i.e., it is imprinted with a time after which it causes its detonating or fragmenting. Such a projectile is effective because of the fragments or the pressure wave of the explosives, which are distributed in space within a conical area. The time of fragmentation is chosen to be such that the fragments or the pressure waves cover the area of uncertainty of the position of the target at the calculated impact time. The imprinted time is the calculated flight time of the projectile to the ideal impact point, less the lead time. The latter can be constant or can be optimally calculated on the basis of the conditions at the time.
The described method has the disadvantage that the available destructive potential must be distributed over the relatively large range of the target uncertainty area, which reduces the effect of a hit. An improvement in this respect is achieved by means of a projectile with a proximity fuse. In general, this is adapted to the relative velocity between the target and the projectile, which is determined by Doppler measurements. Detonating takes place when the relative velocity value, which decreases in proximity to the target, falls below a preset value. A direct hit is not preempted by this. As a rule, fragmentation of the projectile takes place closer to the object than with the time-imprinting method, which results in a higher probability of destruction. However, the proximity fuse requires measuring and signal processing on- board the projectile.
Another possibility of improvement consists in programming the projectile in flight. After launching, determination of the position of the target is continued. Because of this the location of the target can be determined with increasing accuracy until the calculated time of impact. From this it is possible in turn to derive the optimum time-imprinting. If the projectile is equipped with a receiving device and is designed in such a way that at launch it is not only time-imprinted with a mean value, but can also be individually set, it is possible to inform every single projectile in flight at what time it is to fragment. German Patent Publication No. 2,348,365 describes a weapons system which can affect the fuse of a projectile in flight. It comprises a pulse transmitter which can send data to the fuse in the projectile via a transmitting antenna. Among other things, the fuse in the projectile has an electronic receiving device for these data. The data contain the individual address, so that only a particular fuse is addressed, and correction values for a running counter. Detonation takes place when a particular count has been reached. By correcting the count, it is therefore possible to advance or retard the detonation time. Thus, this method results in a reduced target uncertainty zone and an adapted time advance. However, if it arises that the target and the projectile will cross at a relatively large distance, there is nothing else to do but to have the projectile fragment early so that fragments reach the vicinity of the target at all. The destructive potential of these few fragments will hardly suffice to render the target harmless.